Friction element, a clutch facing, and method and apparatus for making same



1964 F; LOMBARDY ETAL 7 FRICTIQN ELEMENT, A CLUTCH FACING, AND METHOD AND APPARATUS FOR MAKING SAME Filed April 6, 1959 2 Sheets-Sheet 1 INVENTORS. FRANK LOMBARDV ROBERT M LAMBERT agqwx W A TTORNE Y Jan. 21, 1964 F. LOMBARDY ETAL 3,118,527

FRICTION ELEMENT, A CLUTCH FACING, AND METHOD AND APPARATUS FOR MAKING SAME 2 Sheets-Sheet 2 Filed April 6, 1959 INVENTOR. FRA/V/f LUMBARDY BY HUBER 7 M L AMBEKT ATTOR/VE Y United States Patent 3,118,527 FREQTIQN A QLUTQH FACING, AND IvIETHQD AND AlhARAEUS FQR MAKH'QG SAME Frank Lomhmdy, Somerville, and Robert M. Lambert,

North Piainz'ield, Ni, to .lolins-Manville Corporatlon, New Yuri-z, N.Y., a corporation of New York Filed Apr. 6, 1959, fier. No. 864,415) 17 Claims. {QL 192-1437) This invention relates to improvements in friction elements and their methods of production. More particularly, it concerns friction elements, such as clutch facings, of the circular-wound or spirally wound type and improved methods of making such friction elements.

the manufacture of large-sized clutch facings in the range of 15 inches in diameter and larger, it has been found extremely difiicult, if not impossible, to successfully employ the circular-winding method using straight, wire-reinforced yams. The apparent reason for this is that when such yarns are wound in convolutions (the technique employed in the circular-winding method) to form disks in the size range aforementioned, the straight wire does not permit the yarn to yield under the internal stresses developed during subsequent curing steps and this frequently results in warping of the finished disk. To a large extent, the problem of warping has been overcome by the improvements in the methods for fabricating large size rriction elements as described in U.S. Patent No. 2,724,671. The improved methods of that patent include a step of crimping the yarns so that when they are wound on a r. andrel, the undulations or corrugations formed by crim ing extend radially within the spiral convolutions of the wound blank. This crimping enables the yarns to assume generally random positioning in the blank to alleviate internal stresses developed during curing and permits substantially warp-free, finished friction elements to be produced.

While the crimping technique disclosed in U.S. 2,724,671 is useful in eliminating the tendency of a finished largesized clutch facing to warp, it has been diificult in operations conducted on a commercial scale at high rates of production to wind the erimped yarns into a blank and at the same time retain the corrugations formed by crimping. in order to prevent the crirnped yarns from straightening during the winding operation, it has been found that very little pressure or tension can be exerted on the crimp-ed yarns, or the crimps will be removed, thus mitigating the beneficial results of the patented methods. As a result, the blanks formed by this method have in practice been very loosely wound and consequently must be handled with great care to prevent their falling apart during subsequent handling prior to the curing operation.

The present invention concerns improvements in the i ethods disclosed in Patent No. 2,724,671 and, accordi gly, an object of this invention is to provide a method of making a friction facing of the type referred to wherein the problems previously encountered are overcome.

Another object of this invention is to provide a friction element of the type referred to which is exceptionally strong, highly resistant to wear, and subject only to substantially uniform wear over the friction faces thereof under high temperature operation as well as being free from warpage or any tendency to warp when fabricated or used.

A further object of this invention is to provide a method of making large-sized, warp-free friction disks of the circular-wound type using crimped, wire-reinforced, fiber yarns without adversely affecting the potential advantages which can be obtained from the use of crimped yarns in the subject procedures.

A still further object of this invention is the provision of a method for making spirally Wound blanks for fric- "ice tion disks of the type referred to at improved production rates, using crirnped wire-reinforced fiber yarns by which the crirnps are retained in the yarns while at the same time producing a firm, easily handled blank.

These and other objects will be apparent from the following detailed description in conjunction with the attached drawing in which:

FIG. 1 is a perspective view showing diagrammatically apparatus for conducting the improved methods of the invention;

FIG. 2 is a fragmentary view showing yarn strands used in practicing the invention;

EEG. 3 is an edge view of a completed blank formed on the winding mandrel of the apparatus of FIG. 1 and showing the disposition of yarns therein;

FIG. 4 is a cross-sectional view of the blank on the winding mandrel taken along lines d4 of FIG. 3;

FIG. 5 is an enlarged, fragmentary plan view showing the frictional surfaces of a completed clutch facing;

FIG. 6 is an enlarged, fragmentary cross-sectional view of the clutch facing shown in FIG. 5, taken on lines 6-6 of PEG. 5;

PEG. 7 is a perspective view showing diagrammatically an alternative arrangement of apparatus for conducting the improved methods of the invention;

FIG. 8 is a plan view of an alternate arrangement of a winding mandrel and driving roll in respect to the crimping rolls; and

FlG. 9 is a plan view of a beveled mandrel and correspending drive roller for obliquely compressing and winding the crimped strand.

in general, the improved process forming the subject matter of this invention comprises treating a plurality of wire-reinforced fiber yarns with an impregnating solution, crimping the yarns after the impregnating solution has dried by passing them between a pair of crimping gears, compressing and winding the criniped yarns onto a winding mandrel, in a manner to obtain random positioning of the yarns on the mandrel such that the depths of the corrugations formed by crimping extend in the same general direction as the axis of the winding mandrel, and subsequently finishing the blank thus formed to provide the resultant friction element. 7

Referring now to the drawing and more particularly to P18. 2 thereof, a preferred form of yarn for practicing this invention is shown, the individual strands being designated by the numeral ll. Preferably, each individual strand 11 is otbained by twisting together two strands of asbestos yarn 12 having a suitable cotton content for strength, with one strand of wire 13. While the resulting individual wire reinforced fiber strand 1 1 is illustrative of the type of yarn that may be employed in practicing this invention, other combinations can be used in which the number of strands of wire or fiber, or the types of wire or fiber may be varied. Brass wire may be used, but other wire or combinations of wire may be used in place of or in conjunction with the brass Wire.

Treatment of the yarns prior to the crimping and winding operations more fully described hereinafter is preferably accomplished as described in the U.S. Patent No. 2,724,671. Thus, the yarns are impregnated with an appropriate binder represented by the stippling 14 in FIG. 1 by running the yarns through a vat containing the impregnating solution. The impregnating solution may be any of the well-known binders such as thermosetting resins, natural or synthetic rubber, drying oils or inorganic binders such as calcium silicate or combinations of these. Also, the solution may include friction particles of metal, ground hard rubber, or the like. After such impregnation, the strands are dried and brought together or .assembled such as by passing them through a ring of appropriate size in a relatively loose bundle to form a composite strand in which the individual strands extend generally in the direction of the length of the composite strand. The number of individual wire-reinforced strands which are assembled to form the composite strand may vary depen ing on the thickness of the friction disk desired. Alternatively, the process of this invention could be carried out using only a single strand instead of the composite strand as described.

After the wire-reinforced fiber yarn strands have been impregnated, dried, and grouped together to form a composite strand designated generally by the numeral 15, they are passed between a pair of crimping gears 16 and 17 to produce a crimped or corrugated tape shown generally by the numeral 18 in FIG. 1. The crimping gears 16 and 17 are of a type well-known to the art and do not form any part of this invention in and of themselves. It is preferred, however, that the number of crimps or undulations per unit length be approximately five per inch. While this number of undulations per inch can be varied, it has been found that the number of undulations should not be reduced below two per inch in order that satisfactory results may be obtained.

In order that the description to follow hereinafter as well as the depending claims may be clearly understood, it is to be noted that the crimped yarn 18, upon passing from the crimping gears 16 and 17, takes an undulated or corrugated form having three dimensions, i.e., the dimension established by the longitudinal extent of the yarns, the dimension established by the number of strands of yarn used to effect the width of the tape 18, and the dimension established by the depth of the corrugations formed by crimping. The latter dimension may also be referred to as the direction of crimping.

After passing through the crimping gears 16 and 17, the crimped composite strand 18 is passed under little or no tension onto a winding mandrel 19 having a pair of radially extending diskalike end walls 21 and 22 and rotatably driven by frictional engagement through the crimped composite strand 18 by a toothed drive roller 23, which roller is synchronized to be driven with the same peripheral speed as gears 16 and 17. It is to be noted that the axes of rotation of the mandrel 19 and the roller 23 are on lines which extend transversely, preferably perpendicularly, to the direction of crimping and further, that the plates or disks 21 and 22 on the mandrel 19' are spaced axially to a distance substantially equal to the axial thickness of the drive roller 23. Because of the perpendicular positioning of the mandrel 19 and drive roller 23 with respect to the direction of crimping, the crimped composite strand 18 is compressed transversely to the direction of crimping or transversely to the dimension established by the depth of the corrugation as it is wound onto the mandrel 19. Moreover, since the individual strands 11 forming the composite strand 18 are loosely retained in alignment, the transverse compression thereof onto the Winding mandrel 19 causes the strands to be positioned randomly on the mandrel, but in a manner that the depths of the corrugations formed by crimping are preferably disposed generally parallel to the axis of the winding mandrel. Thus, as the winding progresses, a relatively firm, dense blank will build up of several convolutions of the yarn, with the crimped corrugations being retained therein and extending generally axially Within each of the convolutions. In addition,

there will be some tendency for the convolutions to receive radial crimps by the teeth on the drive roller 23. These radial crimps will become more pronounced in the outer convolutions of the blank, and being superimposed onto the axially crimped yarn as efiected by crimping gears 16 and 17, will enhance the random but uniform distribution of yarn in the blank. Thus, it will be seen that it is preferred to employ a toothed roller 23 through the principal advantages of the invention could be obtained without this specific feature. 7

As may be seen in FIG. 7, the mandrel is mounted upon '4 a pivotable support 31 suitably connected to a fluid motor in the form of an air cylinder 32. Such arrangement permits the mandrel 19 to be restrained in respect to the drive and compressing roller 23 and yet accommodate the increase in diameter of the wound and compressed strand body on mandrel 19.

FIG. 7 further illustrates a guide member 30' having a configuration for guiding the composite crimped strand 18 from crimping rolls 16 and 17 to a position of proper orientation with the mandrel 19 and the driving and compressing roll 23. It is to be noted that the transverse position of the direction of crimping is attained even though the crimping gears 15 and '17 are in parallel alignment with the mandrel 19 and roller 23, so that the crimped yarn is, as in the case of FIG. 1, wound into convolutions about an axis generally parallel to the dimension defined by the depth of the corrugations.

In the preferred method, the crimped strand is com pressed in a direction transverse and substantially per pendicular to the direction of crimping. However, it will be apparent that the crimped strand may be compressed, prior to or as an initial step in the process of rewinding as described above, in a direction oblique to the direction of crimping without departing from the spirit or scope of applicants invention, such oblique compression being encompassed within the term transverse as employed here m.

It will also be understood that the term axis generally parallel to the dimension defined by the depth of said corrugations as employed in the description and the appended olairns includes any axis within 45 of parallel alignment with the said dimension.

Oblique compression of the crimped strand 18 may be attained by advancing the strand after it passes from the crimping gears 16 and 17 between the mandrel 19 and drive roller 23 if the latter are positioned obliquely to the axes of the crimping gears 16- and 17, indicated in phantom in FIG. 8.

Oblique compression may also be attained by employing a beveled mandrel 19 and a correspondingly beveled and oppositely or complementarily arranged driving roller 23 forming a pair of matched frusto-conical disks as shown in FIG. 9.

Of course, such oblique compression may also be at tained by varying the position of the outlet 29 of the guide member 31 shown in PEG. 7, in respect to the mandrel and driving roll.

By the above described steps of winding and commassing a crimped strand formed from a regularly patterned strip, a finished product is obtainable having the advan tages of a product made from interlacing and irregularly braided strand, Without interlacing. This results not only from retention but also from an increase in the number of the crimps or corrugations in the finished product and from the fact that the individual strands 11 are inter spersed in an irregular pattern within the composite strand 18 after compressing and rewinding.

The improved, unexpected results of this invention now be realized in view of the above. Prior to this in-' vention the crimped strand was rolled directly onto an independently driven mandrel as described in the aforementioned US. Patent No. 2,724,671. By so Winding the crimped composite strand directly onto a mandrel, the tension in the strand, in order to get proper compacting of the blank as it was being formed, resulted in straightening out of the corrugations. This defeated the purpose of crimping, or, if less tension was applied to retain the crimping, a loose, diificult-to-handle blank resulted. In the present invention, however, the crimped composite strand 18 may be compactly wound onto the mandrel 19 without exerting any tension whatsoever in the strand as it passes from the crimping gears 16 and 17. This is possible since the crimping gears 16 and 17 feed the crimped yarn without tension to the synchronized-driveroller 23, which compresses it onto the driven winding mandrel 19 transversely to the direction of crimping, the yarn being confined axially of the mandrel by the disks 21 and 22, the desired degree of compactness for the blank being obtained without damage to the corrugations formed by crimping.

The resulting annular disk 24 consists of a quantity of the crimped wire-reinforced yarn arranged upon itself in convolutions 25 to form a blank of the desired size in which the corrugations 26 formed by crimping extend generally axially within the convolutions as seen in FIGS. 3 and 4. Also, the tendency for the convolutions to receive radial crimps due to the teeth on the drive roller 23, especially toward the outer convolutions of the blank is manifested in the outer windings of the blank.

After the blank has been formed as described above, it may be finished in a number of ways to arrive at the final friction element. Preferably, the blank is placed in a mold and compressed in an axial direction to densify the blank prior to curing. Before curing, the blank may be redipped in the impregnating solution or otherwise impregnated with the same or a different solution, drained and allowed to dry. As in the first impregnating step, various friction imparting filler materials may be added to the solution, in which case the second impregnation should be performed before compressing the blank. The densified, cured blank has characteristics as indicated in the cross-section detail in FIG. 6.

The cured blanks thus produced may be finished in any of the usual ways such as subjecting them to baking, grinding, drilling and counterboring operations. In the final friction disks, as shown in FIGS. 5 and 6, the crimps or corrugations in the yarns are largely retained, the yarn being disposed in the convolutions 25 in which the crimps in the yarn define generally axial corrugations. The yarn is held in the disk formed in the hard cured binder matrix which, as illustrated at 2.7 in FIG. 5, fills the spaces surrounding the wire and fiber, it being understood that the binder matrix thus referred to includes such friction particles as may have been incorporated in either the first or second impregnating steps. Part of the wire 13 and fiber content 12 of the yarn is exposed at the friction surfaces of the finished disk to render visible at these surfaces the generally axial corrugations defined in the convolutions by the crimps in the yarn. As a result of the corrugations, the exposed fiber and wire content is distributed somewhat randomly, but is uniformly compacted, over the friction surfaces as well as throughout the remainder of the disk body as illustrated in FIG. 5. Because of the improved method of forming the disk blank in accordance with this invention and the retention of crirnping obtained thereby the random distribution with uniform compacting of fibers, wire and friction particles is greatly enhanced. This produces a friction element having more uniform wear and friction characteristics than any heretofore provided by the circular-wound method.

Having provided a complete description of the invention in such manner as to distinguish it from other inventions and from what is old, and having provided a description of the best mode contemplated of carrying out the invention, the scope of patent protection to be granted the invention is defined by the following claims.

What we claim is:

l. in a method of making a friction element, the steps comprising: crimping wire-reinforced yarn to form corrugations extending transversely of the longitudinal extent of said yarn; compressing the crimped yarn; and winding the crimped yarn in convolutions about an axis generally parallel to the dimension defined by the depth of said corrugations.

2. In a method of making a friction element, the steps comprising: crimping wire-reinforced yarn to form corrugations extending transversely of the longitudinal extent of said yarn; and compressing the crimped yarn in a direction transverse to the dimension defined by the depths of said corrugations and winding the crimped yarn in 6 convolutions about an axis generally parallel to the dimension defined by the depth of said corrugations.

3. A method of making a friction element comprising: impregnating wire-reinforced yarn with a binder; crimping the impregnated yarn to form corrugations extending transversely of the longitudinal extent of said yarn; compressing the crimped yarn; and winding the crimped yarn in convolutions about an axis generally parallel to the dimension defined by the depth of said corrugations.

4. A method of making a friction element comprising: impregnating wire-reinforced yarn with a binder; crimping the impregnated yarn transversely to form corrugations therein; compressing the crimped yarn in a direction transverse to the dimension defined by the depth of said corrugations; and winding the crimped, compressed yarn in convolutions about an axis generally parallel to the dimension defined by the depth of said corrugations.

5. A method of making a friction element comprising: impregnating wire-reinforced yarn with a binder; crimping said wire-reinforced yarn to form corrugations extending transversely of the longitudinal extent of said yarn; simultaneously compressing and winding the crimped yarn in convolutions about an axis oblique to the dimension defined by the depth of said corrugations to form a blank; impregnating the blank with a binder; further compressing the impregnated blank; and curing the compressed, impregnated blank.

6. A method of making a friction element comprising: impregnating wire-reinforced yarn with a binder; drying and crimping the impregnated yarn transversely to form corrugations therein; compressing, and winding the crimped yarn in convolutions about an axis oblique to the dimension defining the depth of said corrugations to form a blank, further compressing the blank; and curing the compressed, impregnated blank.

7. A method of making a friction element comprising: impregnating wire-reinforced yarn with a binder; drying and crimping the impregnated yarn transversely to form corrugations therein; compressing the strip; and winding the crimped yarn in convolutions about an axis parallel to the dimension defining the depth of said corrugations to form a blank; further compressingthe blank; and curing the compressed, impregnated blank.

8. In a method of making a friction element, the steps comprising: forming a strip width of hardenable binder impregnated and dried fiber yarn; crimping the strip width in a direction transverse to the width of the strip; compressing the strip width; and winding the crimped strip width about an axis in a manner that the successive layers of compressed strip width are inclined with respect to said axis.

9. Apparatus for forming a friction element body from a strip of reinforced yarn comprising, in combination: a pair of crimping elements adapted to crimp said strip and form corrugations extending in a direction transverse to the strip width; a winding mandrel for winding and receiving the crimped strip, said mandrel having an axis of ro tation; means for rotating said mandrel; and compressing means for compressing the crimped strip width, in a direction transverse to the dimension defining the depth of the corrugations, about said mandrel.

10. The apparatus as described in claim 9 which further comprises a guide for directing the crimped strip to said mandrel and said compressing means.

11. The apparatus as described in claim 9 wherein said winding mandrel and said compressing means cooperatively comprise a pair of complementary cylindrical disks.

12. The apparatus as described in claim ll wherein the compressing disk is serrated.

13. The apparatus as described in claim 9 which further comprises a fluid motor to restrain said winding mandrel in respect to said compressing means and yet accommodate the increase in diameter of the body as the strip is wound thereon.

14. The apparatus as described in claim 9 wherein said Winding mandrel and said compressing means cooperatively comprise a pair of complementary frusto-conical disks.

15. Apparatus for forming a friction element body from a strip of reinforced yarn, comprising in combination: crimping means for crimping said strip in a direction transverse to the strip width to form corrugations in the strip; compressing means for compressing the crirnped yarn in a direction transverse to the dimension defining the depth of the corrugations and which direction is parallel to the strip width; and a Winding mandrel for winding and receiving the crimped and compressed strip.

16. A friction element produced according to the method recited in claim 1.

17. A preform disk adapted for compression axially thereof to fabricate a friction element, said preform disk comprising: hardenable binder impregnated and dried 8 strip material of Wire-reinforced yarn arranged in convolutions, the strip material having crimped undulations with the depths of the undulations being disposed obliquely of said disk.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A METHOD OF MAKING A FRICTION ELEMENT, THE STEPS COMPRISING: CRIMPING WIRE-REINFORCED YARN TO FORM CORRUGATIONS EXTENDING TRANSVERSELY OF THE LONGITUDINAL EXTENT OF SAID YARN; COMPRESSING THE CRIMPED YARN; AND WINDING THE CRIMPED YARN IN CONVOLUTIONS ABOUT AN AXIS GENERALLY PARALLEL TO THE DIMENSION DEFINED BY THE DEPTH OF SAID CORRUGATIONS.
 16. A FRICTION ELEMENT PRODUCED ACCORDING TO THE METHOD RECITED IN CLAIM
 1. 